This invention relates to the security of electronic devices.
Portable devices such as laptops and mobile phones are valuable and hence attractive to thieves. Thieves might want the devices for their intrinsic value, or because they are configured to provide access to certain functions. For example, a mobile phone might be stolen with a view to selling the hardware, or with a view to using any available credit to make phone calls using the phone. It is also becoming increasingly common to pay for goods through a mobile phone account. If a phone is stolen then the thief could try to buy goods using the account associated with the phone. Portable computers often provide access to confidential data that might be of value in addition to the intrinsic value of the computer hardware.
Various approaches have been taken to improve the security of portable devices. One approach is to require a user to enter a password before the device can be activated. This provides a certain level of security, but it is inconvenient for a user to enter a password every time they want to use a device.
Another approach is described at http://www.msnbc.msn.com/id/15444447/. This involves wireless communication between a mobile phone and a dedicated card. The phone can be configured to lock automatically when it is moved to more than a pre-set distance (8, 20 or 40 m) away from the card. If the user of the phone keeps the card in a bag or pocket, the phone recognizes when the card moves too far away and locks automatically to prevent someone else from making a call. This system has the disadvantage that it involves dedicated hardware which would significantly increase the cost of the phone.
Lockitnow™ software available from:                http://www.blueshareware.com/lockitnow.aspcan run on a computer and allow the computer to be locked automatically after a period of inactivity when a particular Bluetooth-equipped device is not in range. This approach has the advantage that it uses existing hardware, and enhances security using only additional software. However, the software runs on the computer at the application level. In order to identify which Bluetooth devices are in range it must either (a) instruct the computer's Bluetooth hardware to perform a scan for nearby devices, and to then allow time for the scan to be completed, or (b) instruct the computer's Bluetooth hardware to attempt to make a connection to a specific device and then await the result of the connection attempt. These processes take a significant length of time, and require ongoing communications between the hardware and the application levels. They are therefore not well suited to making frequent checks on the proximity of a particular Bluetooth-equipped device. Conversely, if a stolen computer is to be locked promptly then it is desirable to check frequently whether the particular Bluetooth device is still in range. Furthermore, supporting ongoing communications consumes significant battery energy.        
There is therefore a need for an improved security mechanism.